/**
 *    Copyright (C) 2014 MongoDB Inc.
 *
 *    This program is free software: you can redistribute it and/or  modify
 *    it under the terms of the GNU Affero General Public License, version 3,
 *    as published by the Free Software Foundation.
 *
 *    This program is distributed in the hope that it will be useful,
 *    but WITHOUT ANY WARRANTY; without even the implied warranty of
 *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *    GNU Affero General Public License for more details.
 *
 *    You should have received a copy of the GNU Affero General Public License
 *    along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 *    As a special exception, the copyright holders give permission to link the
 *    code of portions of this program with the OpenSSL library under certain
 *    conditions as described in each individual source file and distribute
 *    linked combinations including the program with the OpenSSL library. You
 *    must comply with the GNU Affero General Public License in all respects for
 *    all of the code used other than as permitted herein. If you modify file(s)
 *    with this exception, you may extend this exception to your version of the
 *    file(s), but you are not obligated to do so. If you do not wish to do so,
 *    delete this exception statement from your version. If you delete this
 *    exception statement from all source files in the program, then also delete
 *    it in the license file.
 */

#pragma once

#include "mongo/db/catalog/collection.h"
#include "mongo/db/commands.h"

namespace mongo {

    /**
     * The explain command is used to generate explain output for any read or write
     * operation which has a query component (e.g. find, count, update, remove, distinct, etc.).
     *
     * The explain command takes as its argument a nested object which specifies the command to
     * explain, and a verbosity indicator. For example:
     *
     *    {explain: {count: "coll", query: {foo: "bar"}}, verbosity: "executionStats"}
     *
     * This command like a dispatcher: it just retrieves a pointer to the nested command and
     * invokes its explain() implementation.
     */
    class CmdExplain : public Command {
    public:
        CmdExplain() : Command("explain") { }

        virtual bool isWriteCommandForConfigServer() const { return false; }

        /**
         * Running an explain on a secondary requires explicitly setting slaveOk.
         */
        virtual bool slaveOk() const {
            return false;
        }
        virtual bool slaveOverrideOk() const {
            return true;
        }

        virtual bool maintenanceOk() const { return false; }

        virtual bool adminOnly() const { return false; }

        virtual void help( stringstream& help ) const {
            help << "explain database reads and writes";
        }

        /**
         * You are authorized to run an explain if you are authorized to run
         * the command that you are explaining. The auth check is performed recursively
         * on the nested command.
         */
        virtual Status checkAuthForCommand(ClientBasic* client,
                                           const std::string& dbname,
                                           const BSONObj& cmdObj);

        virtual bool run(OperationContext* txn,
                         const string& dbname,
                         BSONObj& cmdObj, int options,
                         string& errmsg,
                         BSONObjBuilder& result,
                         bool fromRepl);

    };

}  // namespace mongo
